Move MailOptions to smtp.go

This struct is used by both the server and the client.

backend.go

@@ -27,43 +27,6 @@ type Backend interface {
 	NewSession(c *Conn) (Session, error)
 }
 
-type BodyType string
-
-const (
-	Body7Bit       BodyType = "7BIT"
-	Body8BitMIME   BodyType = "8BITMIME"
-	BodyBinaryMIME BodyType = "BINARYMIME"
-)
-
-// MailOptions contains custom arguments that were
-// passed as an argument to the MAIL command.
-type MailOptions struct {
-	// Value of BODY= argument, 7BIT, 8BITMIME or BINARYMIME.
-	Body BodyType
-
-	// Size of the body. Can be 0 if not specified by client.
-	Size int64
-
-	// TLS is required for the message transmission.
-	//
-	// The message should be rejected if it can't be transmitted
-	// with TLS.
-	RequireTLS bool
-
-	// The message envelope or message header contains UTF-8-encoded strings.
-	// This flag is set by SMTPUTF8-aware (RFC 6531) client.
-	UTF8 bool
-
-	// The authorization identity asserted by the message sender in decoded
-	// form with angle brackets stripped.
-	//
-	// nil value indicates missing AUTH, non-nil empty string indicates
-	// AUTH=<>.
-	//
-	// Defined in RFC 4954.
-	Auth *string
-}
-
 // Session is used by servers to respond to an SMTP client.
 //
 // The methods are called when the remote client issues the matching command.

smtp.go

@@ -15,3 +15,40 @@
 //
 // Additional extensions may be handled by other packages.
 package smtp
+
+type BodyType string
+
+const (
+	Body7Bit       BodyType = "7BIT"
+	Body8BitMIME   BodyType = "8BITMIME"
+	BodyBinaryMIME BodyType = "BINARYMIME"
+)
+
+// MailOptions contains custom arguments that were
+// passed as an argument to the MAIL command.
+type MailOptions struct {
+	// Value of BODY= argument, 7BIT, 8BITMIME or BINARYMIME.
+	Body BodyType
+
+	// Size of the body. Can be 0 if not specified by client.
+	Size int64
+
+	// TLS is required for the message transmission.
+	//
+	// The message should be rejected if it can't be transmitted
+	// with TLS.
+	RequireTLS bool
+
+	// The message envelope or message header contains UTF-8-encoded strings.
+	// This flag is set by SMTPUTF8-aware (RFC 6531) client.
+	UTF8 bool
+
+	// The authorization identity asserted by the message sender in decoded
+	// form with angle brackets stripped.
+	//
+	// nil value indicates missing AUTH, non-nil empty string indicates
+	// AUTH=<>.
+	//
+	// Defined in RFC 4954.
+	Auth *string
+}